She invests, writes about investing and makes money. She’s 15.

Six years ago, stock whiz Maya Peterson sold her American Girl doll for $100. She used the money to buy shares in Mattel, the toy company that manufactures the dolls.

She was 9 years old.

“I made a huge mistake with that one because Mattel stock has plummeted,” Maya said.

“I think it’s at $18 right now, and I bought it at $35. I still have it.”

Maya, 15, of St. Paul, has expanded her stock portfolio over the past six years. Among her current holdings: Johnson & Johnson, Pepsi, Berkshire Hathaway, Nestle and Gilead Sciences.

She recently wrote a book called “Early Bird: The Power of Investing Young,” which was published last month by Amazon.

“The whole purpose of the book is to really make investing more accessible and make it just seem easy and fun, which it is,” Maya said. “It’s not really a hard concept once you get used to it.”

DOING HER HOMEWORK

Maya got into investing through her father, Gunnar Peterson, who designs software systems. On the drive to and from ballet practice, the two would listen to the “Motley Foolery” podcast, she said.

Before Maya could buy any stocks, however, she had to read “Growing Money: A Complete Investing Guide for Kids” by Gail Karlitz.

“I was told I had to read a chapter a week before I was allowed to start investing,” she said. “That’s where I was first introduced to the concept of compounding, and that’s what really got me started.”

Maya invests in products she knows and understands. Take Pepsi, for example.

“The cool thing about Pepsi is that they actually make more money with their chips than their drinks, which I never knew,” she said. “I picked Pepsi because I love Sun Chips. Cheddar Sun Chips are my favorite — that’s how I pick most of my stocks.”

When she was 10, Maya wrote a blog post for the Motley Fool Stock Advisor website explaining “why Mattel was a better stock pick than Hasbro,” she said. (Now Hasbro, which was trading at around $92 Friday, is rumored to be considering a takeover of Mattel).

That same year, she and her father began attending the Berkshire Hathaway annual shareholders meeting in Omaha, Neb.; they haven’t missed a meeting since.

“We stand in the line every year at 4:30 in the morning and wait for the doors to open at 8:30, and then get to go and sit and watch Warren Buffett and Charlie Munger speak all day,” she said.

In 2013, Maya, then age 11, was the youngest person ever to apply and be accepted to attend the Motley Fool’s “College Women and Investing” conference.

By the time she was 14, Maya had another first to add to her résumé: the first female to present to Google’s investing club at the company’s headquarters in Mountain View, Calif.

Maya started her own investment blog called “Compounding Snowballs” in 2016.

The title comes from her favorite investor, Buffett, the CEO and chairman of Berkshire Hathaway, who said: “Life is like a snowball. The important thing is finding wet snow and a really long hill.”

TRUST IN TANGIBLES

Berkshire Hathaway (BRK-B) is one of her favorite stocks, she said, because it’s “a safe company, and it’s run by a huge investor who knows what he’s doing.”

Buffett “invests in a whole bunch of companies that you can relate to and are consumer staples — things that aren’t going to go anywhere anytime soon,” Maya said. “He just helped me figure out where I wanted to go because I can relate to his mindset when it comes to investing.”

Maya, a freshman at Mounds Park Academy, applied for a summer internship at the Motley Fool. They turned her down “because (she) was in eighth grade,” Maya said, but invited her to consult via videoconferencing once a week with a team of investors on their “Fools in Schools” initiative focused on getting teens to invest.

In her spare time over the summer, Maya decided to write her book. She said she saw a need for an investment book for people between the ages of 12 and 25 written by another young person.

Maya recommends that young investors begin by looking around their house for products produced by companies that might be good investments.

“Who sells those light bulbs? Everyone uses light bulbs,” she said.

“Four years ago, I bought Johnson & Johnson (JNJ),” Maya writes in the book. “I bought Johnson & Johnson because I’m a dancer and I would use their toe tape on a daily basis. … I went through about one roll a week, meaning over 52 weeks at a cost of $3.99, they made $207.48 from one customer and one product by the end of the year.”

She said she has made $160 so far on that investment.

MATCHING FUNDS

Maya interviewed a number of investors for the book, including David Gardner, one of the founders of Motley Fool.

Gardner told Maya that good investors are like sports fans. “They are going to be a fan whether their team wins or loses that day,” he told her. “(Good investors are not) going to sell their stock whether or not it goes up or down, today, this week or even this year because they’re in it to win it over the only term that counts, which is the long term.”

Maya, a Boston Red Sox fan, continues the analogy in her book: “When your team makes a mistake, you stick with them,” she writes. “Just because the Red Sox lose a game or two doesn’t mean you are suddenly a Yankees fan.”

Maya and her parents have worked out a deal: Any money that Maya invests in the stock market, they will match dollar-for-dollar.

“It’s very generous of them,” Maya said. “The nice thing about investing is that money will grow no matter how much you put in. If you just get the right stock, it will hopefully compound over time, so if you put in $100, and it’s a really good stock, like Berkshire Hathaway, it’s hopefully going to rise and do well.”

Because she is a minor, the Petersons bought the stocks and hold them for Maya.

One of her latest purchases is Gilead Sciences, a bio-tech company that recently purchased Kite Pharma — “KITE is their ticker symbol,” she said — which produces cancer treatments that train a patient’s immune cells to attack tumors.

She likes the stock so much, in fact, that she recently bought a share for her mother as a birthday present.

‘BUSINESS IN HER BLOOD’

Her mother, Ginnie Peterson, is the owner of Crocus Hill Studio. She teaches flower design classes and workshops and runs the small studio florist business in St. Paul.

“Maya grew up in an entrepreneurial family,” Ginnie Peterson said. “Both of her grandfathers and her great-grandparents were also entrepreneurs in everything from making artificial limbs to owning hotels. Being interested in numbers and business is in her blood.”

Maya wrote, designed, formatted and published the book on her own. She even designed the cover and collected cover blurbs.

“Everyone thinks that we are Tiger Parents, which could not be further from the truth,” Ginnie said. “I didn’t even read the book until last Thursday. My input was not wanted.”

“We sat down with her and said, ‘Well, what do you want to do?’ ” Ginnie said. “She said ‘I’m in A.P. history, I’m teaching myself trigonometry, I’m in pre-calculus. No. If I have to do that, it’s another six months, and half of this material is going to be stale. I’m tired of working on it. I just want to get it out the door.’ ”

When her father offered to help format the book, Maya declined, Ginnie said.

“She said, ‘I want this to be mine. This is my project, not your project. I don’t need you to do this,’ ” Ginnie said. “It’s been kind of impossible to help her, which is why she wrote a book when she was 15, and I didn’t.”

Maya is a great role model for other young women, her mom said.

“Empowering young people, especially young women, is a huge gift,” she said. “To get started this early just gives women choices that I wish that we had all had.”

Investing is one way for teenagers to feel “like they have power and importance in this world.”

“When you invest, you become a part owner of a company,” Ginnie said. “That’s a lot of power. If you’re a part owner of Exxon, you can vote on whether they’re drilling or not, which is a lot more than slamming your fist on the table and being frustrated with how the world is going.”

Maya Peterson said she is investing for the long-term.

“I hope it will be for retirement, and I can retire early, or have the ability to,” she said. “I think I want to work for most of my life and keep busy, but I want to have a little safe pocket of money — not being overly rich, but just having some safety.”

As she writes in her book: “The main reason I invest is because of the lifestyle and my hopes for the future. I’m not talking about fancy caviar or a nice house in the Caribbean.”

And as Ginny Adams, a longtime Fergus Falls investor, says in Maya’s book: “It’s much better than slaving in a hamburger place.”

IF YOU GO

Maya Peterson, the author of “Early Bird: The Power of Investing Young,” will read from and sign books from noon to 4 p.m. Dec. 10 at Addendum Bookstore in St. Paul. For more information, call 651-330-3096.